WATER just like that (mizu, sui 水 ) is not a kigo in Japan but a nonseasonal topic.

But since water is a constant necessity throughout the year, there are many detailed phenomenon used as kigo for it. And in olden times with no tabwater, this comodity was really important for the continuation of life.

Let us go through the seasons.
I also add some Japanese kigo with the word WATER as part of the description of something else.

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

The goodwill of the God of Water is very important to a ricegrowing and farming society.

. water in spring, haru no mizu 春の水 .
shunsui 春水、mizu no haru 水の春
"water in spring" refers to water getting warmer and more pleasant. With the snowmelt, rivers, ponds and lakes get full and the rays of the sun reflect pleasantly on it. It is the water of life for all beings.

mizu-uri 水売 (みずうり) vendor of water
hiyamizu uri 冷水売（ひやみずうり） vendor of cold water
koorimizu uri 氷水売り vendors of "ice water"
This was an important job in the Edo period, when there were no supermarkets or vending maschines on every corner.
They usually started their job around the 5th lunar month.
..... koori uri 氷売 (こおりうり) vendor of ice blocks

toshiyori no hiyamizu 年寄りの冷や水 to do something imprudent for an old person
derived from this habit.

水売りは一つか二つ錫茶碗
水売りは一つか二つ鈴茶碗
mizu-uri wa hitotsu ka futatsu suzu chawan

the water vendor
has one or maybe two
tin cups

Tin cups did not break easily and kept the water cool.
The vendors were dressed in fancyful robes, to look cool themselves.
They drew water from deep wells, but it was soon warm in the hot climate of summer in Edo.

"Enchin, a priest from Nara, was told in a vision to "Look for the clear water origin of the Yodo river". In a long search, he stumbled upon a place deep in the forest greenery where a mist, like a belt of white clouds, hung over a waterfall at the foot of Mt. Otowa."

According to the legend, Enchin received a vision that said he would find at the source of the Yodo river, a clear source of water. During his search Enchin came across a hermit named Gyoei. Gyoei was a old priest practising ascetism and he gave Enchin a piece of wood possessed by the spirit of the Kannon Bosatsu. This was then carved into the likeness of the Kannon and Enchin then enshired the image in a small thatched roofed hut.

This was the begining of Kiyomizudera. The legend also says that the hermit disappeared, and that when Enchin later found the hermit's sandals on top of the mountain, he realized that he had actually been speaking with a manifestation of the Kannon. On the other hand, the hermit may just have wanted some peace and quiet.

The legend continues that Sakanoue Tamuramaro, one of the emperor's leading generals came upon Enchin while deer hunting. The blood of a stag was thought to ease the pain the childbirth, and Tamuramarro's wife was about to give birth. Enchin spoke of the cruelty of killing animals (forbidden in the Buddhist tradition) and his speech so moved Tamuramaro that to repent, Tamuramaro underwrote the construction of a proper sanctuary. (Another story is that he disassembled his home and gave it to the temple, building a new house to replace it).

In 794 the emperor Kammu moved his capital to Kyoto and gave Tamuramaro his throne hall as a reward for his military service. As a devout worshipper of Kannon he proceeded to donate the building to Enchin for a new main hall. The building stood until 1629 until it was destroyed by fire. Today's Main Hall has roof made of cypress, not the traditional tile, in remembrance of originally being part of the emperor's palace. Most of the buildings today were rebuilt by Iemitsu Tokugawa, the 3rd shogun of the Tokugawa Shogunate, in 1633.

Water, which is crucial to our survival has qualities that far transcend it's most basic functions. Looking at some of it's characteristics one realizes that is far more than a "thirst quencher".

Water has the ability to adapt itself totally to it's environment. When the temperature gets too high it becomes steam and it changes to ice when things are too cold. It can also change it's shape to conform to that of the container. What is remarkable about water, is that it manages to maintain its identity under the most varied circumstances.

Water is everflowing and always manages to find its level. When something comes in the way it goes around and takes the path of least resistance. On those occasions where an obstacle seems insurmountable it steadily gains strength and force until it finally overcomes.

No matter how high a dam is built on a stream... eventually the stream overflows the dam. There is an unyielding and steady effort that water generates which regards all obstacles, no matter how high or big, as being temporary.

Finally, calm water is like a mirror and gives a picture of all that is around. Conversely troubled waters only reflect the turmoil within. When a person approaches a problem with calm and composure then like the reflection on calm water he sees everything. So also when a problem causes turmoil then like the troubled water on confusion is seen.

Imagine an intellect as calm, a will as relentless and indomitable and a personality as adaptable as water and you will have envisioned a MIND LIKE WATER>

Nobuyuki Yuasa explains: "The bathtub was placed outside the house, and water was flowing into it probably through a bamboo pipe"; The Year of My Life: A Translation of Issa's Oraga Haru, 2nd Edition (Berkeley: Univ. of California Press, 1972) 58. Issa copies this haiku into his journal Oraga haru ("My Spring") with the prescript, "Mount Tokage." In other texts he prefaces it with "In Mount Tokage's mansion." Mount Tokage lies to the west of Issa's home village of Kashiwabara. In this location the Shinto god Tokage's festival is celebrated; Issa zenshu^ (Nagano: Shinano Mainichi Shimbunsha, 1976-79) 6.168, note 74.